The present invention relates to a passive system for regulating temperature in an enclosure exposed to ambient temperature extremes, and in particular to a system which passively cools the interior of a structure exposed to extreme heat.
The interior spaces of structures exposed to extreme heat are typically cooled by active refrigeration (i.e., air conditioning) and evaporative cooling systems. Unfortunately, such systems demand a substantial amount of electric or another type of external power which generates substantial operating costs in addition to the initial cost of the system. Refrigeration systems use almost as much electrical energy as the energy they remove in cooling the interior space of a structure. Evaporative cooling systems also use substantial amounts of electrical energy to power fans and pumps, and require constant replenishment of their water supply.
The cost of active cooling systems is not always prohibitive in structures designed for human habitation or use, such as homes, office buildings, factories and the like. However, cooling systems are often desirable in other types of structures where the installation and operating costs of active cooling systems cannot by justified, such as relatively small or remote structures designed to house livestock or electrical or fiber-optic equipment. It is often not feasible to bring electricity to a remote structure or to provide for the generation of electricity on-site, or to provide an alternate source of power. As a result, active cooling systems often cannot be used in situations in which some form of temperature control is highly desirable.
In an attempt to avoid the deficiencies of active cooling systems in remote installations, certain systems have been developed which attempt to provide cooling by passively radiating heat to the night sky. Such systems typically employ a large thermal mass, such as a quantity of water, which absorbs heat during the day to minimize the increase in the temperature of the interior of the structure. At night, a form of thermal coupling is provided to the roof so that the heat content of the thermal mass is reduced by radiation from the roof to the night sky. During the day, of course, the thermal couple must thermally isolate the thermal mass from the roof so that the thermal mass is not directly heated by solar radiation. One such system is disclosed in U.S. Pat. No. 4,913,985, assigned to the assignee of this application.
The Achilles heel of existing passive cooling systems is the complex thermal coupling mechanism required between the thermal mass and the roof. The above-referenced patent discloses a system of hoses which rely on suction, effectively limiting the technique to relatively small structures. Other such systems rely on movable covers or other mechanisms such as fans which must be powered and which defeat the objective of a truly passive cooling system which operates without an external power source.